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2004 Toyota 4Runner Buildup - New-School 9-Inch

Anyone who's broken a ring-and-pinion in a late-model Toyota has to admit it's a weak link in an otherwise legendary drivetrain. While you can always replace the OEM gear set with aftermarket parts, Currie Enterprises has figured out a way to sling an F9 rear axle under your Toyota.

The F9 can be ordered as shown with FJ Cruiser/4Runner link brackets or with Tacoma leaf-spring perches.

The Currie F9 is several upgrades in one. It's like killing ants with a sledgehammer. The most obvious benefit is that you'll ditch your weak link, the Toyota ring-and-pinion set, and replace it with the proven beef of a Ford 9-inch.

"We designed the F9 housing to be stronger than a standard-style Track 9," John Currie said. "Not only is it stronger, but it will accept a Trophy Truck-style 10-inch ring gear." Most of us don't need a 10-inch ring gear, but we all benefit from the gigantic range of ring-and-pinion ratios and differentials available for the Ford 9-inch third member.

Next, the F9 housing can accept 3- or 3-1/4-inch-diameter axle tubes. The tubes can be ordered with different wall thicknesses. The housing ends are compatible with the OEM Toyota axle bearings. Inside the F9, Currie Enterprises has produced 35-spline axle shafts that are also compatible with the OEM Toyota axle bearings. The housing-end-and-axle-shaft combo means that the Currie F9 for your late-model Toyota is compatible with your ABS, VSC, and TRAC systems. It's also compatible with your stock Toyota brakes. Finally, the Currie F9 is available in custom widths. Yes, a Currie F9 for your Toyota brings several upgrades on board in one fell swoop. Ants, meet sledgehammer.

Our 2004 Toyota 4Runner was a perfect candidate for the F9 upgrade. The addition of a Total Chaos long-travel frontend meant that the front track width exceeded the rear by several inches. On top of that, we wanted to change our ring-and-pinion sets to better match the oversize tires we'd fitted a while back. Instead of the stock open rear differential, we wanted a real locker that would provide traction no matter what. We hadn't broken a rear ring and pinion or snapped an axle shaft...yet. This rig gets taken on a lot of solo off-road excursions, so a backcountry breakdown is at the top of the "avoid" list.

Most of the time, I like turning my own wrenches. This time, I was happy to snap the photos while Currie Enterprises' Tony Sato took care of the mechanicals. I had a tall order: I wanted the F9 to achieve the same bump travel as the stock Toyota rear end had. Since the F9 is physically larger than the 'Yota unit, achieving full bump travel was going to be a tricky task. Thanks to Currie's manufacturing capability and Tony's mechanical skills, full bump travel was pulled off in style.

Once the F9 was installed, it was time for a test drive. It took about a block and a half to realize a new sway bar was in order, specifically a Currie Antirock.

After the F9 and Antirock were in place, the front gears needed swapping. A visit to American Gear Shop in La Habra, California, filled that need. American Gear's Hector Ambriz is meticulous and knowledgeable: exactly the kind of guy you want for a gear swap.

Read on for the details. We'll cover the F9 this time, and concentrate on the Antirock and the front gear swap next month. With a new-school 9-inch under the 4Runner, backcountry confidence is at an all-time high.